2.4 Notes for Particular Systems

On systems ‘*-*-aix[34]*’ shared libraries are disabled by default, since
some versions of the native ar fail on the convenience libraries
used. A shared build can be attempted with

./configure --enable-shared --disable-static

Note that the ‘--disable-static’ is necessary because in a shared build
libtool makes ‘libgmp.a’ a symlink to ‘libgmp.so’, apparently for
the benefit of old versions of ld which only recognise ‘.a’,
but unfortunately this is done even if a fully functional ld is
available.

ARM

On systems ‘arm*-*-*’, versions of GCC up to and including 2.95.3 have a
bug in unsigned division, giving wrong results for some operands. GMP
‘./configure’ will demand GCC 2.95.4 or later.

Compaq C++

Compaq C++ on OSF 5.1 has two flavours of iostream, a standard one and
an old pre-standard one (see ‘man iostream_intro’). GMP can only use the
standard one, which unfortunately is not the default but must be selected by
defining __USE_STD_IOSTREAM. Configure with for instance

./configure --enable-cxx CPPFLAGS=-D__USE_STD_IOSTREAM

Floating Point Mode

On some systems, the hardware floating point has a control mode which can set
all operations to be done in a particular precision, for instance single,
double or extended on x86 systems (x87 floating point). The GMP functions
involving a double cannot be expected to operate to their full
precision when the hardware is in single precision mode. Of course this
affects all code, including application code, not just GMP.

MS-DOS and MS Windows

On an MS-DOS system DJGPP can be used to build GMP, and on an MS Windows
system Cygwin, DJGPP and MINGW can be used. All three are excellent ports of
GCC and the various GNU tools.

Microsoft also publishes an Interix “Services for Unix” which can be used to
build GMP on Windows (with a normal ‘./configure’), but it’s not free
software.

MS Windows DLLs

On systems ‘*-*-cygwin*’, ‘*-*-mingw*’ and ‘*-*-pw32*’ by
default GMP builds only a static library, but a DLL can be built instead using

./configure --disable-static --enable-shared

Static and DLL libraries can’t both be built, since certain export directives
in ‘gmp.h’ must be different.

A MINGW DLL build of GMP can be used with Microsoft C. Libtool doesn’t
install a ‘.lib’ format import library, but it can be created with MS
lib as follows, and copied to the install directory. Similarly for
‘libmp’ and ‘libgmpxx’.

cd .libs
lib /def:libgmp-3.dll.def /out:libgmp-3.lib

MINGW uses the C runtime library ‘msvcrt.dll’ for I/O, so applications
wanting to use the GMP I/O routines must be compiled with ‘cl /MD’ to do
the same. If one of the other C runtime library choices provided by MS C is
desired then the suggestion is to use the GMP string functions and confine I/O
to the application.

Motorola 68k CPU Types

‘m68k’ is taken to mean 68000. ‘m68020’ or higher will give a
performance boost on applicable CPUs. ‘m68360’ can be used for CPU32
series chips. ‘m68302’ can be used for “Dragonball” series chips,
though this is merely a synonym for ‘m68000’.

OpenBSD 2.6

m4 in this release of OpenBSD has a bug in eval that makes it
unsuitable for ‘.asm’ file processing. ‘./configure’ will detect
the problem and either abort or choose another m4 in the PATH. The bug
is fixed in OpenBSD 2.7, so either upgrade or use GNU m4.

Power CPU Types

In GMP, CPU types ‘power*’ and ‘powerpc*’ will each use instructions
not available on the other, so it’s important to choose the right one for the
CPU that will be used. Currently GMP has no assembly code support for using
just the common instruction subset. To get executables that run on both, the
current suggestion is to use the generic C code (CPU ‘none’), possibly
with appropriate compiler options (like ‘-mcpu=common’ for
gcc). CPU ‘rs6000’ (which is not a CPU but a family of
workstations) is accepted by ‘config.sub’, but is currently equivalent to
‘none’.

Sparc CPU Types

‘sparcv8’ or ‘supersparc’ on relevant systems will give a
significant performance increase over the V7 code selected by plain
‘sparc’.

Sparc App Regs

The GMP assembly code for both 32-bit and 64-bit Sparc clobbers the
“application registers” g2, g3 and g4, the same way
that the GCC default ‘-mapp-regs’ does (see SPARC Options in Using the GNU Compiler Collection (GCC)).

This makes that code unsuitable for use with the special V9
‘-mcmodel=embmedany’ (which uses g4 as a data segment pointer), and
for applications wanting to use those registers for special purposes. In these
cases the only suggestion currently is to build GMP with CPU ‘none’ to
avoid the assembly code.

SunOS 4

/usr/bin/m4 lacks various features needed to process ‘.asm’
files, and instead ‘./configure’ will automatically use
/usr/5bin/m4, which we believe is always available (if not then use
GNU m4).

x86 CPU Types

‘i586’, ‘pentium’ or ‘pentiummmx’ code is good for its intended
P5 Pentium chips, but quite slow when run on Intel P6 class chips (PPro, P-II,
P-III). ‘i386’ is a better choice when making binaries that must run on
both.

x86 MMX and SSE2 Code

If the CPU selected has MMX code but the assembler doesn’t support it, a
warning is given and non-MMX code is used instead. This will be an inferior
build, since the MMX code that’s present is there because it’s faster than the
corresponding plain integer code. The same applies to SSE2.

Old versions of ‘gas’ don’t support MMX instructions, in particular
version 1.92.3 that comes with FreeBSD 2.2.8 or the more recent OpenBSD 3.1
doesn’t.

Solaris 2.6 and 2.7 as generate incorrect object code for register
to register movq instructions, and so can’t be used for MMX code.
Install a recent gas if MMX code is wanted on these systems.